DESCRIPTION: Plus-stranded RNA viruses, which pose significant risks to human health and cause major losses for agriculture, depend heavily on host factors to replicate in infected cells. The roles of the subverted host factors in virus replication are currently poorly understood due to the lack of tractable virus-host systems. To advance rapidly our understanding of virus-host interactions during viral replication, the investigator has developed the powerful Tomato bushy stunt virus (TBSV)-yeast model system that led to the identification of numerous host factors affecting viral replication. This application is aimed at dissecting the roles of three RNA-binding host proteins: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the p68 DEAD-box RNA helicase homolog Dpb2 and translation elongation factor EF-1alpha (Tef1/2p), all of which bind to TBSV RNA and also known to interact with Hepatitis C virus, West Nile virus, dengue 4 virus and hepatitis A virus RNAs, suggesting that host factors might play similar roles in replication of these viruses. The advantages of tombusviruses for replication studies are numerous, including (i) their simple genomes and robust replication; (ii) similarity of TBSV replicase proteins to proteins of important pathogens, such as HCV, West Nile virus and other flaviviruses and pestiviruses; (iii) availability of in vitro replication assays developed in the Investigator's laboratory; and (iv) the development by the investigator of an efficient yeast-based TBSV replication system. In addition, a recent genome-wide screen including 95% of all yeast genes identified host genes that affected TBSV accumulation. Based on these advances, TBSV is a premium model system to study the roles of host factors in virus replication in eukaryotic hosts. Due to the central role of virus replication in viral pathogenesis, the proposed studies on host RNA-binding proteins involved in virus replication promise to advance our understanding of the viral replication process and to lead to identification of new antiviral targets. These and similar studies are needed urgently, because our current knowledge on host factors involved in virus replication and in viral pathogenesis is incomplete. Knowledge of virus-host interactions and the roles of host RNA-binding proteins might reveal new drug targets and lead to development of novel antiviral strategies. The tractable in vitro and in vivo TBSV system developed by the investigator could prove beneficial to studies of other, less amenable RNA viruses. [unreadable] [unreadable] [unreadable]